One of the most enjoyable things about reviewing
cables from Purist Audio Design, other than the opportunity to hear some
outstanding cables, was the chance to chat with and learn a lot from one of the
pioneers of hifi cable design, Jim Aud. Jim came to south Texas to work on the
South Texas Nuclear Project (one of the last US nuclear power plants) and stayed
to build cables.

Launching Purist Audio Design in 1986, Jim takes a
holistic approach to designing cables, considering all parameters which
influence the sound of a cable, not just a few parameters in isolation. Purist
employs two full-time engineers, who work with Jim in designing new cables. They
use computer modeling to steer them towards a particular design, and have a
machine shop and construction facility that lets them build prototypes to
finalize a design. Extensive use of beta testing provides the customer feedback
so vital to successful cable implementation. Purist has about 50 beta testers
around the country, and two or three bands that try Purist cables under
stressful real-world conditions. Feedback from beta testers is used to modify
designs into a final commercial product line.

Jim stressed that advances in material science had
made it possible to improve the design of cables. Purist was a pioneer in the
use of cryogenic treatment, which is now commonplace in cable manufacturing; but
which Purist began to use in 1995. They now combine cryogenic treatment with
immersion in a strong magnetic field to align the crystal structure of their
conductors.

Purist uses a combination of copper, silver, and
gold as conductors for the audio signal. Since Purist uses RCA plugs of their
own design, they can make them from the same metals used in the conductors, to
ensure minimum signal loss. Although Purist's RCA plugs look pretty ordinary (no
locking collar here), throughout my tests, they always gripped the input jacks
firmly and never even thought about coming out prematurely. If all RCA plugs
worked this well, we probably wouldn't have ever needed the locking collar
design.

Purist's most advanced technology uses a light
source to illuminate the cable's dielectric, which produces an ethereal
three-dimensional soundfield that sounds like surround sound from two channels.
The Radiant Light Source (RLS) cables basically add this optical illumination to
the company's award-winning (the absolute sound's 2003 Golden Ear Award
Winnerfor Interconnect and Loudspeaker Cables) Dominus cables. The
Purist web site describes the RLS cables thusly: "The Radiant Light Cable
System, newly introduced by Purist Audio Design in 1998, is the only system of
its kind in the world. It takes the already superb Dominus cable and adds a
special form of radiant-optical fiber. These optical fibers are illuminated by a
specially designed light source and radiate light around the conductors. The
light changes the properties of the insulation surrounding the conductors, thus
minimizing distortion in music reception.

The result can best be described as a dramatic lowering of the cable's noise
floor. Micro dynamics that previously lay buried in low-level background noise
are revealed. The nuance of musical emotion is laid bare as never before. The
stunning improvement achieved through the Radiant Light system affords the
reality of a musical experience unlike any enjoyed until now.

I asked Jim if the RLS design had any similarity to
the battery-biased designs like Audioquest's Big Cat series of cables, but he
indicated it was a different concept. He described the concept of dielectric
biasing as older technology developed by Western Electric in the 1930s. And in
case you were wondering, the RLS technology comes at a price: $7350 for a
one-meter pair of RCA-terminated interconnect cables, with an extra $2500 for
the RLS power supply.

A basic design goal in Purist cables since their
early days has been cables that are extremely quiet. Cables don't generate noise
like electronics do; instead, they pick up physical vibrations from the sound
and other sources, and EMI and RFI from a variety of sources, including the sun.
The noise picked up by cables doesn't sound like hum or hiss, but instead is a
masking effect on the output signal. I don't know if it's measurable, but it's
one of those distortions that become obvious when they're removed. It's somewhat
like washing a window; you sometimes don't know how much clearer your view
through a window can be until you wash it. Maybe the first washing removes half
the accumulated dirt, which still gives a dramatic improvement. And then when
the second washing removes the remainder of the dirt, the clarity of the image
is surprising but obvious. That's similar to the effects I heard from Purist's
cables; their budget Musaeus cables were clearly quieter than anything I had
previously heard, which produced abundant musical detail without resorting to
unnatural high-end emphasis. Then, when I heard the much more advanced Venustas
cables, the noise was dramatically lower, as though someone removed two more
layers of dirt from the window. The effect is not subtle. A welcome side effect
is that you don't have to play music as loud to hear details of the performance.

A hifi system can pick up vibration through cables
hanging loose or on the floor, through the equipment itself, or (in some cases)
through tubes, which are subject to microphonics. As you might expect, rigid
cables tend to pass more vibration. Purist has used two types of shielding to
prevent noise pickup from physical vibration. The first was a fluid jacket that
surrounded a cable and provided a built-in shock absorber. More recently, a
compound called Ferox has been used. Jim describes the fluid shield as more
euphonic sounding, while the Ferox is more neutral and extended, with a 6 db
improvement in quietness.

Electromagnetic interference (EMI) and radio
frequency interference (RFI) problems have been around a long time, and are
getting steadily worse as wireless networking becomes more prevalent. Other
sources of RFI like cell phones and cordless phones make the home environment
even more polluted by electromagnetic energy. Even the sun's radiation, and
re-radiation from your house, can generate noise that a hifi system can pick up.
Purist's solution to the EMI and RFI problem has been electrical shielding.
Fortunately, the Ferox compound is also an effective RFI shield, and is
connected to the inner shield and RCA plug at the source end of the cable. But
even their AC power cords, which don't use Ferox shielding, seem to be amazingly
quiet. When I first plugged in the Venustas power cords (in a system that was
already using Musaeus power cords), I was stunned at how much quieter they were,
and thus how much more detail they passed through. And that's just the power
cords! An attractive spinoff of their effective shielding is that Purist cables
don't need to be elevated off the floor.

In a follow-up e-mail, Jim Aud expanded on his "…
personal design goals for the different series of cables. Museaus was designed
to give Audiophiles the most bang for the buck, Venustas is designed to give
Audiophiles the most sonics and still have WAF "Wife acceptance factor" and try
to hold cost in line. Dominus is all about the sound, end of story. RLS
is technology advancements due to material science."

Purist cables are not cheap, but they are very
laborious to construct. Jim revealed that a pair of his Dominus RCA interconnect
cables take 100 hours to build. So even though they sell for $5250 for a
one-meter pair, much of that cost goes to pay for the skilled labor needed to
construct the cables.

If any one area of the hifi industry is fraught with
bogus engineering claims and junk science, it's cables. Several self-proclaimed
experts have declared that cable design is just a matter of simple engineering,
and that the performance of cables can be predicted from their standard
electrical parameters (resistance, capacitance, and inductance). Jim described a
demonstration he had conducted in Japan, where he built several cables, keeping
the RLC parameters the same, but changing the geometry of the cables. The sound
of the different designs was radically different.

I asked Jim about contact cleaners, and he warned
that some of the more advanced compounds might be harmful over the long run by
attracting dirt or lint. He recommended using good old fashioned alcohol to
clean connectors.

Purist has a sizeable network of experienced dealers
who use a simple technique to demonstrate Purist cables: they let prospective
customers listen to broken-in cables on their systems. Most of them become
actual customers. Then, the satisfied customers augment the sales force with
word-of-mouth recommendations. If there's no dealer in your area, Purist will
sell direct. Unlike many companies that try to isolate themselves from their
customers, Purist talks to theirs. Jim indicated that a typical cable sale
involves an average of five calls from customers.

I'm an avid browser on eBay and AudioGon, where lots
of interesting audio gear is sold. During my conversation with Jim, it dawned on
me that I had never seen any Purist Audio Design cables being resold.
Considering how many are sold, that's amazing, and probably indicates how
satisfied customers are over the long-term.

Jim closed with a heads-up that Purist was planning
something really special for its 20th anniversary. That should be
worth waiting for! Fortunately, 2006 is not far off.